paper 2 things i need to remember

Question 1

FORMATION OF AMINE:
1-bromoethane + ammonia–>
2-bromopentane + ammonia–>

Answer 1

Question 2

further substitution of haloalkanes to amines can cause a secondary or tertiary amine, hence why we need excess ammonia to stop this. write the equation for:
bromoethane + ethylamine–>

Answer 2

Question 3

what is an alpha amino acid?

Answer 3

amino acid with carboxyl + amine groups on same carbon

Question 4

what are delocalised pi electrons?

Answer 4

electrons shared over more than 2 carbons

Question 5

why can cyclohexene react with bromine without HCC but not benzene?

Answer 5

1) cyclohexene pi electrons are localised, in benzene they are delocalised
2) cyclohexene has a greater pi electron density
3) cyclohexene is more able to polarise electrophiles

Question 6

why is phenol more reactive than benzene?

Answer 6

1) the lone electron pair on the oxygen on phenol is delocalised into the pi ring
2) phenol has a greater pi electron density
3) phenol is more able to polarise electrophiles

Question 7

why is nitrobenzene less reactive than benzene

Answer 7

1) -NO2 group is electron-withdrawing
2) electron density of pi cloud decreases
3) less able to polarise electrophiles

Question 8

test for phenol + observations

Answer 8

add Br2 water, white ppt forms + Br2 water decolourises

Question 9

draw products of phenol + HNO3 (nitration)

Answer 9

2-nitrophenol/ 4-nitrophenol + H2O

Question 10

activating/ electron-donating groups (2,4-directing)

Answer 10

-OH + -NH2 (increase pi electron density)

Question 11

deactiviting/ electron-withdrawing groups (3,5- directing)

Answer 11

-NO2 (decreases pi electron density)

Question 12

how to identify specific carbonyls

Answer 12

add 2,4-DNP, recrystallise + filter orange ppt, test melting point + compare to a database

Question 13

why do nucleophiles react with carbonyls?

Answer 13

C=O bond is polar bc oxygen is more electronegative, carbon is electron-deficient + nucleophiles are attracted to electron-deficient atoms

Question 14

why are carboxylic acids soluble in water?

Answer 14

they can form hydrogen bonds with water due to having the O-H bond

Question 15

order of reactivity with carboxylic acids, acyl chlorides, acid anhydrides

Answer 15

acyl chlorides (Cl very electronegative so C more elctron-deficient)> acid anhydrides> carboxylic acids

Question 16

reaction of acyl chloride to carboxylic acid + observations

Answer 16

RCOCl + H2O –> RCOOH + HCl (violent reaction, steamy fumes of HCl formed)

Question 17

what is nmr + how does it work?

Answer 17

nuclear magnetic resonance: a nucleus has 2 different spin states with different energies- with correct radio frequency, nuce.us can absorb energy + flip between these states (resonance), allowing identification of specific chemical environments

Question 18

what is TMS used as?

Answer 18

STANDARD to show frequencies of different absorptions

Question 19

why are deuterium-containing compounds e.g/ CDCl3 used as solvents?

Answer 19

deuterium doesn’t show up on NMR spectrum bc of even number of particles in its nucleus

Question 20

definition of condensation polymerisation

Answer 20

joining of 2 monomers in a condensation reaction, removing a small molecule usually water

Question 21

what are biodegradable polymers?

Answer 21

broken down by microorganisms into water, CO2 + other biological molecules

Question 22

what are photodegradable polymers?

Answer 22

contains bonds that are weakened when light is adsorbed to start degredation e.g. C=O

Question 23

what is a sigma bond?

Answer 23

head-on overlap of orbitals directly in a line between bonded atoms

Question 24

limitations of TLC

Answer 24

compounds often have similar Rf values, + unknown compounds have no Rf value for reference

Question 25

stationary + mobile phases of TLC

Answer 25

s: silica
m: solvent
separates by relative adsorption

Question 26

stationary + mobile phases of GC

Answer 26

s: high boiling point liquid
m: inert carrier gas
separates by relative solubility

Question 27

limitations of GC

Answer 27

same as TLC + not all substances will be separated

Question 28

method of purifying organic liquid with separating funnel

Answer 28

1) pour impure mixture into separating funnel, allow to settle (lower density layer on top), open tap + run off aqueous layer
2) add NaCO3 to organic layer to remove acidic impurities.
3) swirl funnel + invert, occasionally opening tap to remove evolved CO2
4) open tap + separate 2 layers + repeat washings of organic layer
5) run organic layer into conical flask + add drying agent e.g. CaCl2 to remove water from organic liquid, til it’s clear
6) decant organic liquid from drying agent + distil, then collect distillate at boiling point of pure liquid

Question 29

method of purification of organic solid by recrystallisation

Answer 29

1) dissolve impure solid in minimum volume of hot solvent, ensuring max recrystallisation
2) cool solution with ice bath, recrystallising organic compound bc insoluble in cold solvent
3) filter under reduced pressure
4) wash solid with cold solvent
5) dry

Question 30

melting point determination of pure solid method

Answer 30

1) seal one end of capillary tube by rotating over hot Bunsen
2) allow to cool and fill about 5mm depth of solid
3) place tube + thermometer into melting point apparatus
4) heat solid slowly, ensuring accurate value, + record temp when solid melts.
5) compare mp value with databook